Numerous core processes of powder and particle technology play a role, particularly in the preparation of starting products, their qualification and feeding to the actual 3D printer. The printing process and materials used determine what is important.
In selective laser sintering (SLS), for example, the starting products are in powder form. The materials used include metal powders such as aluminium and titanium, silicon carbide, thermoplastic polyurethane and polyamide. The SLS powders must have a uniform, relatively small particle size. They are dried and sieved before processing to ensure a homogeneous grain size.
The material requirements for the DED (Directed Energy Deposition) process using metal or ceramic powder are similar. The starting products can be explosive; explosion protection measures are therefore often required.
The classic screening technology is used in adapted variants. For example, the company assonic Dorstener Siebtechnik offers special machines for the ultrasound-assisted screening of fine metal and plastic powders, starting with mesh sizes of 20 µm. The Sonic Speed Screen screening technology works with a combination of high-frequency ultrasound and low-frequency knocker excitation. This enables a high screening capacity to be realised with a small footprint. The Sonic Powder Conditioner can be used to automate metal sieving and preparation for additive manufacturing. The Mini Sonic Screen MSS 150 can also be used for batch processing of small quantities of powder.
If the starting products are thermoplastic filaments such as PLA or ABS, careful drying is required, as with powders. Otherwise, bubbles may form in common printing processes such as fused filament fabrication (FFF). The filaments may also need to be cut to the correct length before printing.
Liquid starting products such as resins used in stereolithography or digital light processing, must also be prepared before printing. Pigments and additives are evenly distributed by shaking or stirring. Impurities are removed by filtration.
Carefully analyse material properties
Quality control is very important in all preparatory processes. Foreign substances that could impair the print quality and durability of the parts to be produced must be removed. In addition to the particle size, the chemical properties and moisture content of the material are also checked. Specialised trade fair exhibitors such as AZO already provide support during the development of 3D printing processes. The company's Technology Centre includes a so-called Toxicontainer. It enables the safe testing of hazardous raw materials used in additive manufacturing. In this safe test room with PPE, glovebox and special air filter system, the materials can be tested under optimal conditions, ensuring maximum protection for the product and operator. AZO also offers a wide range of solutions for the storage, conveying, feeding, conditioning and recovery of plastic and metal materials for additive manufacturing.
After correct preparation and quality control, the material is fed to the printers, for example using special dosing systems for powder feeding. They must ensure an uninterrupted supply to the 3D printers. The product is added via a glovebox, for example, and conveyed under inert gas. Pneumatic and vibration processes, screw conveyor systems and powder nozzles are used here. Resins, on the other hand, are sometimes fed to the printer build chambers via pump systems. A sieve module is usually installed upstream of the actual pressure chamber.
Thinking about safety aspects
IB Verfahrenstechnik, a member of the PIAB Group since 2023, specialises in material flow technology in 3D printing production. IB Additive brand solutions are created from an extensive modular system of ultrasonic screening stations and vacuum conveyors. Thanks to their modularity, existing systems can be easily converted or expanded. Integrated inertisation and residual oxygen monitoring complement the main modules.
The compact ECODustPro 15 WB inert safety vacuum cleaner from Evo Products is also designed for safety in additive manufacturing. Extracted explosive metal dusts are passivated by a liquid bath. The full range of safety features includes a degassing valve, which prevents the build-up of gases and vapours, as well as graduated filtration using H14 cartridge filters and special VA filters. Ex protection is guaranteed in Zone 22.
Process Sensing Technologies PST is addressing another safety aspect with the compact Ntron SIL-O2 oxygen analyser. As a SIL2 device, it is particularly suitable for safety-critical applications. It can be calibrated at the touch of a button and is ready for easy integration.
Perfect coordination between AM and powder handling system
Partnerships between bulk material handling experts and 3D printer manufacturers, such as Volkmann and EOS, are particularly beneficial for the end customer. Together, they have developed a scalable powder handling solution for metal powder that can supply up to six printers. In addition to pre-processing, the solution also includes post-processing, including the preparation of used powder through sieving. This makes it possible to realise a closed powder cycle for fully automatic 24/7 operation. The end user benefits from a single point of contact throughout the entire life cycle of their system and from harmonised AM and powder handling systems.
